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Operations On Rational Numbers (Exercise 5.3) RD Sharma Solutions | Mathematics (Maths) Class 7 PDF Download

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Exercise 5.3         Page No: 5.10 
 
1. Multiply: 
(i) (7/11) by (5/4) 
(ii) (5/7) by (-3/4) 
(iii) (-2/9) by (5/11) 
(iv) (-3/13) by (-5/-4) 
 
Solution: 
(i) Given (7/11) by (5/4) 
(7/11) × (5/4) = (35/44) 
 
(ii) Given (5/7) by (-3/4) 
(5/7) × (-3/4) = (-15/28) 
 
(iii) Given (-2/9) by (5/11) 
(-2/9) × (5/11) = (-10/99) 
 
(iv) Given (-3/13) by (-5/-4) 
(-3/13) × (-5/-4) = (-15/68) 
 
2. Multiply: 
(i) (-5/17) by (51/-60) 
(ii) (-6/11) by (-55/36) 
(iii) (-8/25) by (-5/16) 
(iv) (6/7) by (-49/36) 
 
Solution: 
(i) Given (-5/17) by (51/-60) 
(-5/17) × (51/-60) = (-225/- 1020) 
= (225/1020) 
= (1/4) 
 
(ii) Given (-6/11) by (-55/36) 
(-6/11) × (-55/36) = (330/ 396) 
= (5/6) 
Page 2


 
 
 
 
 
 
 
Exercise 5.3         Page No: 5.10 
 
1. Multiply: 
(i) (7/11) by (5/4) 
(ii) (5/7) by (-3/4) 
(iii) (-2/9) by (5/11) 
(iv) (-3/13) by (-5/-4) 
 
Solution: 
(i) Given (7/11) by (5/4) 
(7/11) × (5/4) = (35/44) 
 
(ii) Given (5/7) by (-3/4) 
(5/7) × (-3/4) = (-15/28) 
 
(iii) Given (-2/9) by (5/11) 
(-2/9) × (5/11) = (-10/99) 
 
(iv) Given (-3/13) by (-5/-4) 
(-3/13) × (-5/-4) = (-15/68) 
 
2. Multiply: 
(i) (-5/17) by (51/-60) 
(ii) (-6/11) by (-55/36) 
(iii) (-8/25) by (-5/16) 
(iv) (6/7) by (-49/36) 
 
Solution: 
(i) Given (-5/17) by (51/-60) 
(-5/17) × (51/-60) = (-225/- 1020) 
= (225/1020) 
= (1/4) 
 
(ii) Given (-6/11) by (-55/36) 
(-6/11) × (-55/36) = (330/ 396) 
= (5/6) 
 
 
(iii) Given (-8/25) by (-5/16)
(-8/25) × (-5/16) = (40/400)
= (1/10)
(iv) Given (6/7) by (-49/36)
(6/7) × (-49/36) = (-294/252)
= (-7/6)
3. Simplify each of the following and express the result as a rational number in
standard form:
(i) (-16/21) × (14/5)
(ii) (7/6) × (-3/28)
(iii) (-19/36) × 16
(iv) (-13/9) × (27/-26)
Solution: 
(i) Given (-16/21) × (14/5)
(-16/21) × (14/5) = (-224/105) 
= (-32/15)
(ii) Given (7/6) × (-3/28)
(7/6) × (-3/28) = (-21/168)
= (-1/8)
(iii) Given (-19/36) × 16
(-19/36) × 16 = (-304/36)
= (-76/9)
(iv) Given (-13/9) × (27/-26)
(-13/9) × (27/-26) = (-351/234) 
= (3/2)
4. Simplify:
(i) (-5 × (2/15)) – (-6 × (2/9))
(ii) ((-9/4) × (5/3)) + ((13/2) × (5/6))
Solution: 
Page 3


 
 
 
 
 
 
 
Exercise 5.3         Page No: 5.10 
 
1. Multiply: 
(i) (7/11) by (5/4) 
(ii) (5/7) by (-3/4) 
(iii) (-2/9) by (5/11) 
(iv) (-3/13) by (-5/-4) 
 
Solution: 
(i) Given (7/11) by (5/4) 
(7/11) × (5/4) = (35/44) 
 
(ii) Given (5/7) by (-3/4) 
(5/7) × (-3/4) = (-15/28) 
 
(iii) Given (-2/9) by (5/11) 
(-2/9) × (5/11) = (-10/99) 
 
(iv) Given (-3/13) by (-5/-4) 
(-3/13) × (-5/-4) = (-15/68) 
 
2. Multiply: 
(i) (-5/17) by (51/-60) 
(ii) (-6/11) by (-55/36) 
(iii) (-8/25) by (-5/16) 
(iv) (6/7) by (-49/36) 
 
Solution: 
(i) Given (-5/17) by (51/-60) 
(-5/17) × (51/-60) = (-225/- 1020) 
= (225/1020) 
= (1/4) 
 
(ii) Given (-6/11) by (-55/36) 
(-6/11) × (-55/36) = (330/ 396) 
= (5/6) 
 
 
(iii) Given (-8/25) by (-5/16)
(-8/25) × (-5/16) = (40/400)
= (1/10)
(iv) Given (6/7) by (-49/36)
(6/7) × (-49/36) = (-294/252)
= (-7/6)
3. Simplify each of the following and express the result as a rational number in
standard form:
(i) (-16/21) × (14/5)
(ii) (7/6) × (-3/28)
(iii) (-19/36) × 16
(iv) (-13/9) × (27/-26)
Solution: 
(i) Given (-16/21) × (14/5)
(-16/21) × (14/5) = (-224/105) 
= (-32/15)
(ii) Given (7/6) × (-3/28)
(7/6) × (-3/28) = (-21/168)
= (-1/8)
(iii) Given (-19/36) × 16
(-19/36) × 16 = (-304/36)
= (-76/9)
(iv) Given (-13/9) × (27/-26)
(-13/9) × (27/-26) = (-351/234) 
= (3/2)
4. Simplify:
(i) (-5 × (2/15)) – (-6 × (2/9))
(ii) ((-9/4) × (5/3)) + ((13/2) × (5/6))
Solution: 
 
 
 
 
 
 
 
(i) Given (-5 × (2/15)) – (-6 × (2/9)) 
(-5 × (2/15)) – (-6 × (2/9)) = (-10/15) – (-12/9) 
= (-2/3) + (12/9) 
= (-6/9) + (12/9) 
= (6/9) 
= (2/3) 
 
(ii) Given ((-9/4) × (5/3)) + ((13/2) × (5/6)) 
((-9/4) × (5/3)) + ((13/2) × (5/6)) = ((-3/4) × 5) + ((13/2) × (5/6)) 
= (-15/4) + (65/12) 
= (-15/4) × (3/3) + (65/12) 
= (-45/12) + (65/12) 
= (65 – 45)/12 
= (20/12) 
= (5/3) 
 
5. Simplify: 
(i) ((13/9) × (-15/2)) + ((7/3) × (8/5)) + ((3/5) × (1/2)) 
(ii) ((3/11) × (5/6)) – ((9/12) × ((4/3)) + ((5/13) × (6/15)) 
 
Solution: 
(i) Given ((13/9) × (-15/2)) + ((7/3) × (8/5)) + ((3/5) × (1/2)) 
((13/9) × (-15/2)) + ((7/3) × (8/5)) + ((3/5) × (1/2)) = (-195/18) + (56/15) + (3/10) 
= (-65/6) + (56/15) + (3/10) 
= (-65/6) × (5/5) + (56/15) × (2/2) + (3/10) × (3/3). 
= (-325/30) + (112/30) + (9/30) 
= (-325 + 112 + 9)/30 
= (-204/30) 
= (-34/5) 
 
(ii) Given ((3/11) × (5/6)) – ((9/12) × ((4/3)) + ((5/13) × (6/15)) 
((3/11) × (5/6)) – ((9/12) × ((4/3)) + ((5/13) × (6/15)) = (15/66) – (36/36) + (30/195) 
= (5/22) – (12/12) + (1/11) 
= (5/22) – 1 + (2/13) 
= (5/22) × (13/13) + (1/1) × (286/286) + (2/13) × (22/22) 
= (65/286) – (286/286) + (44/286) 
= (-177/286) 
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